1. Field of the Invention
The present invention relates in general to the production of bands of crimped fibers. More specifically, the present invention relates to a method and device for conveying crimped fiber during the production process, using air jets.
2. Description of the Related Art
In the process of producing fiber products, such as products produced by spinning, a planar ribbon of crimped fiber (also referred to as a xe2x80x9ctow bandxe2x80x9d) may be produced as an intermediate. For example, a large number of polymer strands may be spun, gathered together in a band and then crimped. After crimping, the tow band is spread back and forth on a slow moving drying conveyor. At the end of the conveyor, the dried tow band is taken off and transported to a baling machine, where the tow band is deposited to form a bale for shipment. For example, acetate tow and polyester tow can be produced in this manner.
Conventionally, the delicate crimped fiber web is dragged over a large number of stationary guides or rollers from the end of the dryer to the inlet of the baling machine. To move the fiber, it must be pulled from the dryer to the baling machine. There is friction between the stationary guides and rollers and the tow band during transportation. The pulling action associated with moving the weight of the tow, and the friction extend the fiber and remove the crimp. The crimp extension is irreversible. That is, the crimp does not return to the fiber after the external forces are removed. The fiber is taken off of the dryer at a slower speed than it is fed to the baler. For example, if the tow is coming off of the dryer at 100 meters per minute and the tow is extended 25% during transportation, then the tow must be pulled into the baling machine at a rate of 125 meters per minute.
The distance the fiber must travel from the dryer to the baling machine varies depending on the relative locations of these two pieces of machinery. Generally speaking, the further the fiber must be transported, the more the crimp in the fiber will be extended. The inlet to the baling machine may be at the same elevation level as the outlet of the dryer. Alternatively, the inlet of the baling machine may be above or below the outlet of the dryer. If the fiber is transported (pulled) uphill, more crimp is removed, and if the fiber is transported (pulled) downhill, less crimp is removed. If there are distance or elevation differences within a single plant, then the quality of the fiber tow produced by that plant will be inconsistent.
To eliminate the problems described above, a belt conveyor or a vibratory shaker conveyor might be considered as fiber transport devices. However, these devices contain a large number of moving parts, are very expensive, very large or unreliable for fiber web transport.
Accordingly, it is an object of the present invention to transport a planar ribbon of crimped fiber while minimizing the friction between the transport device and the fiber.
It is further object of the present invention to transport a planar ribbon of crimped fiber from an origin to a destination while minimizing the pulling force on the fiber at the destination.
It is yet another object of the present invention to transport a planar ribbon of crimped fiber without extending the fiber and removing the crimp.
It is a still further object of the present invention to transport a planar ribbon of crimped fiber in a manner that can maintain consistency in the amount of crimp in the fiber produced throughout a plant, even if the distances and elevations traveled throughout the plant are inconsistent.
The present invention addresses the above objects by providing a method and device for conveying crimped material, which can be used with any type of crimped material having a planar configuration and a ribbon-like form. For example, the present invention can be used with paper, ribbon, synthetic fiber, tow and natural fiber tow.
The present invention provides a method and device for conveying a ribbon of crimped material including an air mover, a plenum connected to the air mover to receive air from the air mover, a series of directional slits and side walls. The directional slits are in fluid communication with the plenum so that air from the plenum exits through the directional slits in a predetermined direction. The directional slits are arranged in a generally planar configuration to form a conveyance track. The side walls are provided on either side of the conveyance track to extend above the conveyance track.
The crimped material may be a planar band of crimped fiber, such as a planar band of crimped acetate fiber. The crimps may extend in an up-and-down direction, normal to the plane of the crimped fiber or in-and-out, parallel to the plane of the crimped fiber.
The plenum may be formed of a pair of elongated support pieces with cutout portions in the elongated support pieces. In this case, the directional slits are formed by air knives fitting into the cutout portions of the elongated support pieces, and the elongated support pieces define the side walls. With the cutout portions, the position of the air knives within the cutout portions can be adjusted to vary the spacing between the air knives. Alternatively, the plenum may be formed from a tubular material having a hollow interior. In this case, the directional slits are cuts formed partially through the tubular material such that the cuts penetrate into the hollow interior of the tubular material.
The directional slits may be positioned at substantially equal intervals along the conveyance track. Further, the directional slits may be substantially parallel to one another.
The device may be modular, with a plurality of generally straight conveyer sections and a plurality of curved conveyer sections. If modular, the device is assembled by selectively connecting the generally straight conveyer sections with the curved conveyer sections. A single air mover may provide air to each plenum or an air mover may be provided for each plenum.